Product Specification

Product Overview

Through-hole ruby bearings are precision-engineered components made from synthetic single-crystal ruby (Al₂O₃ doped with Cr₂O₃). These bearings are designed with a central through-hole structure that allows shafts, pins, or optical fibers to pass through smoothly while minimizing friction and wear. Owing to ruby’s extreme hardness (Mohs 9), outstanding chemical stability, and excellent surface finish, these bearings are widely used in precision instruments, metering devices, fiber optic assemblies, and micro-mechanical systems where stability and long lifespan are critical.

Material and Structure

The bearing body is made of synthetic corundum crystal, grown under controlled conditions to ensure uniform hardness and purity. Chromium doping gives the material its characteristic red color and adds optical clarity and corrosion resistance. The through-hole is precisely machined and polished to achieve micron-level dimensional accuracy and smoothness, ensuring excellent coaxiality and low friction in rotary or oscillating movement.

Typical Parameters

• Material: Synthetic Ruby (Al₂O₃ + Cr₂O₃)

• Hardness: Mohs 9

• Density: 3.98 g/cm³

• Operating Temperature: -60°C to +500°C

• Hole Diameter: 0.05–5.0 mm (customizable)

• Outer Diameter: 0.5–10 mm (customizable)

• Concentricity Tolerance: ≤ 0.003 mm

• Surface Roughness: Ra ≤ 0.02 μm

Key Features

1. Ultra-High Hardness & Wear Resistance – Ruby’s exceptional hardness ensures minimal abrasion, maintaining stable dimensions over years of operation.

2. Smooth and Precise Rotation – The through-hole design and optical-level surface polish guarantee low friction and high rotational accuracy.

3. Chemical & Thermal Stability – Ruby bearings can withstand acids, alkalis, solvents, and high temperatures without deformation or corrosion.

4. Excellent Dimensional Precision – Each bearing is precisely lapped and inspected to meet strict concentricity and parallelism standards.

5. Long Service Life – Even in high-speed or continuous-contact applications, ruby bearings maintain performance and do not require lubrication.

Applications

• Precision Measuring Instruments: Used in dial indicators, micrometers, and flow meters for stable, friction-free movement.

• Fiber Optic and Laser Systems: Serves as alignment and support components in optical connectors and light transmission assemblies.

• Watchmaking and Micro Motors: Provides low-friction pivoting for high-precision miniature shafts.

• Medical and Analytical Equipment: Ensures accurate motion in miniature pumps and sensor mechanisms.

• Aerospace and Defense Devices: Ideal for compact, durable, and vibration-resistant bearing solutions.

Advantages Over Metal Bearings

• No oxidation or rusting

• No magnetic interference

• No need for lubrication

• Higher hardness and smoother operation

• Longer operational lifespan

Quality and Customization

Each through-hole ruby bearing is subject to 100% inspection for dimensions, hole alignment, and surface finish. Custom designs are available for diameter, thickness, and hole geometry to meet unique application needs. Assemblies combining ruby bearings with stainless steel or ceramic housings can also be provided upon request.

FAQ

Q1: What is the difference between a through-hole ruby bearing and a cup ruby bearing?
A: A through-hole ruby bearing has an open bore running through it, allowing a shaft or pin to rotate or slide freely. A cup ruby bearing has a concave seat for point-contact rotation, typically used in jewel pivots and instruments.

Q2: Can through-hole ruby bearings operate without lubrication?
A: Yes. Due to ruby’s ultra-smooth surface and hardness, these bearings can work dry without oil or grease, even in vacuum or cleanroom conditions.

Q3: Are these bearings suitable for high-speed rotation?
A: Yes, within design limits. Ruby’s high hardness and low friction make it ideal for precision rotation, though speed tolerance depends on shaft quality and assembly conditions.

Q4: Can I order custom hole sizes or special shapes?
A: Absolutely. We offer tailor-made ruby bearings with customized hole diameters, countersinks, chamfers, and mounting styles based on your drawings or samples.

Q5: How do you ensure consistency in optical and mechanical performance?
A: All ruby materials are grown under strict crystal growth control, and each part is processed using CNC micro-machining and double-side polishing to guarantee uniformity.